Disorders
of mental functioning produced by varying the
oxygen tension of the atmosphere

Effects of low oxygen atmospheres on normal
individuals

and patients with psychoneurotic
disease

Barach AL, Kagan J

0n Claude Bernard's statement that "the
fixity of the internal environment is the
condition of a free life," Barcroft (ri)
suggested that the organism in gaining constancy
of temperature, hydrogen-ion concentration,
water, sugar and oxygen ultimately reached a
stage of development so that man's higher
faculties could develop. It is evident that
profound biochemical alterations in the body
seriously impair mental functioning. Conversely,
mental and emotional reactions have been shown
by Cannon (17, 18), Pavlov (36), and others to
initiate changes in the organic state of the
organism. The relation between psychic and
somatic processes has been the subject of
considerable contemporary investigation, as
shown by the reviews of Dunbar (20) and
Fetterman (22). In clinical disease, so-called
functional and organic manifestations have often
been separately classified but it is doubtful
whether this division is as valid as it appears;
it may well be that apprehension and
hyperchlorhydria in a patient with gastric ulcer
proceeds from a basic stem that has branched out
into manifestations of both a psychic and
physical character, rather than that the psychic
factor produced the physical change or the
reverse. Whether this be true or not, our
understanding of psycho-pathology must
ultimately be aided by controlled studies of the
effects on mental functioning of altering basic
physiologic processes as well as the study of
physiological reactions initiated by altering
emotional influences.

Interference with a steady supply of oxygen
to the organism has long been known to impair
the functioning of the central nervous sytem.
Paul Bert (14) showed that the effects of high
altitude were principally due to the lowered
partial pressure of oxygen in the inspired air.
Since that time the consequences of anoxia on
bodily and mental functioning have been studied,
at first on high mountains, later in chambers in
which the concentration or pressure of oxygen
was reduced. The growth of aviation has
stimulated additional research on oxygen
deprivation in order to determine at what
altitude flying is attended with harmful
effects. These studies have been extensively
reviewed by McFarland (31,32), and our in
tention is to refer only to those that form a
background for this paper.

The symptoms of moderate oxygen deficiency,
which begins after exposure for two or three
hours to an altitude of 10,000 to 2000 feet, may
be listed as: headache, dizziness, fullness in
the head, parasthesias, impairment in memory and
judgment. The occurrence of these symptoms, as
well as others about to be referred to, led to
the proposal that compulsory oxygen inhalation
be adopted for commercial pilots flying at
altitudes of 50, 000 to 12,000 feet and over,
based on the opinion that "pilot error" may be
in part due to oxygen-want. (Barach 6). The
studies of McFarland and Armstrong (1,2,3)
contribute support to this point of view, which
hss been also upheld by Boothby, Lovelaee and
Mayo (zd). More prolonged exposure leads to
nausea, vomiting, tachycardia, slight fever,
malaise, and the symptoms originally known as
mountain-sickness. From 12,000 to 15,000 feet,
these symptoms are more marked, and above 15,000
feet, serious effects are produced in the
majority of individuals, in both mental and
bodily functioning. A few reports will be
briefly referred to. Table I gives the relation
between oxygen percentage and the corresponding
altitude.

Birley (z) found that pilots after an hour
at 15,000 feet took twice as long to sight a
target, and that firing time was increased and
accuracy diminished. Wilmer and Berens (41)
studied the effect of altitude on ocular
functions and found slight changes between
10,000 and 15,000 feet, and marked changea above
15,000 feet. McComas (30) reported that subjects
with latent esophoria saw double between 10,000
and 15,000 feet. Standard psychological tests
(including sensory perception) at 14,000 feet
showed deviations from the normal after short
exposure (Tanaka, 39), (Lowason, 29), (Dunlop,
21), (Watson, to). In experiments by Barach,
McFarland and Seitz (9), exposure to an altitude
corresponding to 12,000 feet for three hours
resulted in a marked increase in errors in slide
rule exercises in three out of four university
students. Effort on the part of the subjects was
motivated by payment of a small sum for each
correct answer. Lack of emotional control was
also manifested in two of the subjects.
McFarland and Baraeh compared the reaction of
normal individuals to psychoneurotic patients
after inhalation of 10 per cent and 12 per cent
oxygen. Of a group of 40 patients and an equal
number of controls, approximately 70 per cent of
the patients collapsed in 90 per cent oxygen
(corresponding to 20,000 feet), whereas only 94
per cent of the controls were so markedly
affected. Psychological rears revealed a more
marked impairment in the psychoneurotic group.
The rapidity of exposure to low oxygen
atmospheres was shown to exercise a marked
influence by Schwartz (38) who made observations
on the effect of a rapid ascent to 16,000 feet
as compared to a slow ascent. In the former the
subjects recorded an average figure of 905
complaints; in the slow ascent only 59
complaints.

Armstrong (4) exposed young aviators to a
lowered oxygen pressure in a chamber,
corresponding to 12,000 feet, for hours daily
for 6 weeks, and observed the development of
symptoms which were similar to those found in
"aeto-neurotic" aviators, namely, apprehension,
irritability, gastric complaints and a
diminished sense of well-being. Kroetz (28) has
reported in neurotic patients showing vasomotor
instability (in the absence of cardiorespiratory
disease) a lowering of the arterial oxygen
saturation to 88 per cent when a painless
arterial puncture brought about pallor and
sweating. Hicks (26) found a diminished arterial
oxygen saturation in psychoneurotic subjects at
rest, in the absence of vasomotor reactions. The
findings of Kroetz and Hicks have not been
confirmed but they also suggest a relation as
yet unclear between anoxia and apprehensive
states. Haldane (24, 25) during the War pointed
out that soldiers who exhibited the symptoms of
"neurasthenia," fatigue and "shock" were apt
also to show shallow breathing, fatigue of the
respiratory center (shortness of breath on
exertion) and exaggeration of circulatory
reflexes, suggesting to him the possibility that
sriilitary neurasthenia was a more lasting form
of ordinary fatigue due to oxygen-want.
Bareroft, Hunt and Dufton (12) reported that
patients with chronic gas poisoning were greatly
improved, both physically and in respect to
their psychoneurotic tendencies, after one week
in a chamber with go per cent oxygen.

In studies by Barach and Richards (7,10,37)
of the effects of inhalation of 50 per cent
oxygen on patients with chronic cardiac and
pulmonary disease, striking alterations in the
mental state of the patients have been observed.
Coincident with the relief of acute dyspnea,
there is a diminution in restlessness and
apprehension, with an increased tendency to
sleep. However, in patients in whom pre-existing
anoxemia has been severe and prolonged, the
administration of 50 per cent oxygen has at
times provoked irrational states, delirium and
coma beginning with several hours of treatment.
In one case of pulmonary emphysema, relief of
dyspnea and cyanosis was followed by the patient
lapsing into a coma which persisted for six
days. The patient was completely irrational when
aroused. At the end of the sixth day he awoke
cheerful, rational, and alert. Prior to
treatment he had been apprehensive and
depressed; following oxygen treatment he was
optimistic and unworried, as long as the oxygen
concentration in the atmosphere was not
prematurely reduced. It is characteristic of
patients with severe long-standing anoxemia that
a cheerful mental state ensues following the
deep sleep or coma which oxygen treatment
sometimes provokes. When an active delirium
develops soon after oxygen treatment is begun,
the patient may be difficult to control but in
these instances also continuation of oxygen
treatment is followed by resumption of a normal
mental state.

In summary, it may be stated that variations
in the oxygen tension of the blood both above
and below what the organism has been accustomed
to may be attended with profound alterations in
mental functioning. The purpose of the study to
be reported was to observe the effects of
inhalation of 53 per cent oxygen for a
three-hour period in normal individuals and in
psychoneurotic patients, not only in respect to
efficiency of intellectual function, such as
memory and judgment, but also from the point of
view of affective response, mood and emotional
control.

Method of investigation

......

Results

There were no differences in efficiency of
response to the retention and recall test at the
end of the three hour test, between those
subjected to abrupt and those subjected to
gradual exposure to oxygen want, either in the
student or patient group. However, the subjects
almost uniformly noted that the gradual onset of
anoxemia was accompanied by a sense of
well-being, with at times a prolonged feeling of
elation and a diminished frequency of somatic
complaints. These findings are in agreement with
those of Schwartz. Three students described
their reaction to gradual reduction of the
oxygen percentage, which was the second
exposure, as follows:

Mr. B.: "1 feel different from the last
time, you must be giving me an excess of oxygen.
T feel slight elation, my legs are not twitching
like the last time. Last time it seemed like
coming into a different world."

Mr. K.: "I don't have a real headache this
time."

Miss S.: "Last time J felt more dull."

In the 17 medical students exposed to
inhalation'of 13 per cent oxygen for 3 hours,
characteristic complaints were: a mild or severe
frontal headache, slight dizziness,
yawning, sense of oppression, pain in the
joints and epigastrium, tingling sensation in
fingers and toes, jitteriness. Changed
perception of color was observed in some of the
subjects.

Ten of the 57 students (59 per cent) showed
shorter or longer periods of elation during
which facial expression changed; increased motor
activity took place in the form of tapping,
singing, whistling and pressure of speech;
increased productivity, flightiness,
facetiousness, heightened sense of well being
were also observed, all of these symptoms
resembling the hypomanic state. 1'he period of
elation was followed by dullness, drowsiness,
and deep sleep, from which the subject could be
awakened only after repeated attempts. Awareness
of having been asleep was generally absent, and
the ability to distinguish between dream
experiences and reality showed some impairment.
For example, one subject was convinced of having
had several convulsive seizures and remembered
having been surrounded by relatives and
physicians. It was impossible to assure him of
the imaginary nature of this experience.
Lowering the oxygen content precipitated a short
period of elation followed by a pronounced
drowsiness and sleep, as illustrated in the
subjects' own description:

Mr. A.: "It's as if I was drunk. Now it's
worn off. I want to sleep. Then all of a sudden
J catch myself as if I was afraid for some
reason. I feel funny, full in the chest. At the
beginning J felt like in the beginning of
drinking, I felt like being facetious."

Mr. S.: "Either I am getting superabundance
of energy or what, but I am getting
restless."

Mr. P.: "I feel much more clear than when I
came. I have had an emotional disturbance for a
few weeks. I am happier than when I came. J have
not been bothered by any thoughts. I don't seem
to think about it at all." 'Ihe same subject
states later: "J feel dizzy, I have a headache,
my thinking is dull. I have to read one sentence
over l don't know how many times. J want to
study, but my mind seems to be wandering off. I
have no thoughts. Don't bother me, I am
sleepy."

In the remaining 7 of the students (41 per
cent) the period of elation was not observed.
Irritability, dullness resulting in marked
listlessness and especially poor performances on
psychological tests were noted, together with a
changed perception of their own body, such as:
'My ears seem to pull up," "My head feels big
and light." Vague, undefined fears, feeling of
strangeness and detachment from the world were
frequent. It is best illustrated by the
subjects' own description.

Mr. R.: "I feel pretty good, when look at it
all. I feel ton good. My voice is notably bad. I
should not subject you to hearing me." Then
later: "I am restless, my head feels big and
light. The light in the room has different
color. You look pretty icteric. Things look
different. I have not much desire to concentrate
much. I sort of feel a little silly, the way one
feels when one is hysterical. Subjectively, one
feels nothing, semi-detachment, as if you were
not completely responsible."

Mr. 7.: "1 feel like coming out of hypnotic
sleep. The hours pass awfully quickly. The world
looked strange when I came out, it passed away
very quickly." Inability to concentrate was
observed in all cases and was especially marked
after two hours exposure to the lowered oxygen
concentration.

Mr. S.: "I read the last sentence ten times
and I don't know what's all about. I stopped
thinking long ago."

Mr. K.: "I have difficulty in reading, my
head feels heavy." Mispronunciations were
observed several times. They consisted in
omission of letters, as such as "obsinate"
instead of obstinate, "olneraly" instead of
alternately. Objectively, we observed dullness,
lethargy, and listlessness. Complaints of
blankness, apathy and extreme fatigue were
especially pronounced after the experiment.
Subjects described these sensations as
follows:

Mr. N.: "I am awfully darned tired, as if I
should climb back and go to sleep, I don't feel
like doing anything."

Mr. M.: "My mind is not absolutely clear, I
am confused for one thing, I feel a bit dizzy, I
can't think as well as I should, I feel dull
right now."

Mr. B.: "My mind is in a jumble, I can't
think of anything, I got a headache."

With very few exceptions the perception of
time seemed to be affected. Three hours were
estimated by the majority as two, or less. In
the patient group the somatic complaints were
essentially the same as in the student group
with the exception that they were not as
frequent and less pronounced. A great majority
of the patients expressed suspicion that some
stimulating drug, or ether had been added to the
gas mixture. All expressed a fear of death by
suffocation during the 3 hour period. Five of
nine patients had a prolonged period of moderate
or marked excitement, motor restlessness and
overactivity with threatening behavior. Extreme
ovsrproduetivity, lack of inhibitions, and
extremely forward and frank sexual advances were
made. Sensations of well being, exaggerated
self-esteem, and thorough enjoyment of the
situation were the most prominent features. Some
of the subjective observations were:

Mr. S.: "I am afraid. It's like falling
asleep in ether. My breathing puts me to sleep.
I see it relieves tension by breathing. Every
time you breathe you relax. I will smother in a
little while. I feel dizzy. I feel a little
sick. I feel cramps right here in my stomach. I
feel helpless. I am not master of myself. I
shall rip it off. I know I am better than the
average. The other patients would raise Dickens.
1 know how to stop it. Don't you think 1 have
been analyzed pretty well, I know the ropes. I
am getting there. I mean I am beginning to
understand the tricks of subconscious. I am
feeling better. I am enjoying it. I like it here
... With you it would be a double pleasure 11
make a good psychoanalyst. I know as much as you
do. I feel a little smothered. I have the
feeling to rip it open. I bet fellows like me
make better psychoanalysts than you or Dr.
S."

Mr. W.. "The air seems slightly
chloroformed. It's like an incubator the
generator of loosening of thought. I have the
feeling that something. This machine is
stopping, I think you have to go into it. You
and I should be here, we could...

Mr. B.: "I am not bashful in the tent. I
feel a little happy. I feel like I had a lot of
whiskey. I have a headache, the same sort of
headache I get when I am drunk. My breathing
comes in jerks." (Is told the hour of day.)
"Jesus Christ, I thought one hour passed, how
quick. I'll miss the tank."

Mr. B. (after the tent): "Oh boy, Oh boy, I
heard a sound in my head. It seems like a sound
going from one side to another. It's like a lot
of thin fiat lines, pencil lines rising to the
sky. It's hard to describe. It's passing very
quickly. It's like a cavern when it is quiet.
The great silence is worse or almost like a
noise. That's the beat way I can describe it. I
don't fear you, I fear this room less. I feel a
lot relieved of the tension. My headache is
practically gone."

Four patients did not show any period of
excitement. They were irritable, dull and drowsy
by the end of the first hour and remained so
throughout the experiment.

Mr. S.: "Everything seems so distant, so far
away. Whatever I try to think about seems
immaterial. I try to think about it, if air were
not coming I would not do anything about
it."

It must be remarked that no deviation from
usual behavior in the above mentioned patients
was noted when the experiments were conducted in
normal air. After the three hour exposure to low
oxygen was over, the behavior of the patients
did not differ noticeably from that of the
medical students. They were all dull, lethargic
and fatigued. The "repetition and recall" test
described above has proven to be not only an
indicator of purely retentive capacity, but
allowed us some insight into the functioning of
the individual as a whole, since not only the
number of errors but the type of errors and
general behavior during the test were
significant.

The results of these tests on each subject
in the student group is listed in Table II. For
the entire group of medical students the average
number of errors in the control test prior to
the experiment was j6.s while the average after
the experiment was 52.5; that is, for the entire
group there was 45.. per cent more errors as a
result of the anoxia induced. In 2 of rj
students there was no demonstrable impairment in
mental functioning. Our subjects reacted to the
retention and recall testa as did those of
Curran and Schilder (19), who state:

"We come to the conclusion that we deal in
our experiments not only with changes in the
recall, but also with changes in the
organization of traces. Our experiments show
clearly that a change in the trace from
repetition to repetition does not consist merely
of a fading of a trace and the lessening of the
efficiency. It occurs in our protocols again and
again that words and sentences which were not
available at a previous recall become available
at a later recall."

Not only was this true in the teat under
normal conditions, but also after the exposure
to 53 per cent oxygen in all groups. We found
the first three stories exhibited the largest
number of omitted words, these latter
reappearing in the later repetitions of the
story until a certain pattern was established.
This pattern was subsequently maintained with
some variation during the remainder of the
test.

Our experimental findings are further in
accord with those of Curran and Sehilder (19) in
that our student group exhibited a tendency to
replace more complex words with simpler ones
before, as well as after, exposure to 13 per
cent oxygen. In the patient group, however, we
noted a definite tendency to replace simpler
words with stilted, formal, and rarely used
ones.

We found a considerable difference in
rapidity of pattern formation as well as in the
type of errors not only between the student and
patient groupa, but within each group, depending
upon whether the teat was taken before or after
the exposure to 13 per cent oxygen.

The results of the retention and recall test
on each subject in the potient group is listed
in Table III. For the entire group the average
number of errors prior to the experiment was
75,45, while the average number after the
experiment was 60.96, that is, 19.2 per cent
decrease in errors after the exposure to 13 per
cent oxygen. On the other hand, in our student
group we find an increase of 45.4 per cent in
the number of errors after the exposure to 53
per cent oxygen.

Analyzing the errors in the student group,
we find that the number of omitted words
increased after exposure to lowered oxygen. The
chief reason for this increase was the number of
words added to the original story. The added
words are not the result of increased
productivity as they express extreme hesitation,
uncertainty, perseveration, and confabulation.
This latter state is closely related to organic
confusion. The retold stories as a whole were
hazy, or nonsensical at times. Preoccupation
with insignificant details, and elaboration were
frequent. A pattern is not established until
very late and even then showed a greater
variability. Similar results have been observed
in serial drawings of a man (Goodenough test)
after insulin coma, and Metrazol seizures, where
it seemed to be the expression of organic
confusion (23).

Analyzing the errors in the patient group we
find that the number of words omitted before the
experiment was somewhat greater than after
exposure to 13 per cent oxygen; furthermore,
many more words were added beforethe experiment
than after exposure to lowered oxygen. This is
an opposite tendency to that shown in the
student group. The words added by the patients
reflect their usual preoccupations with a
resultant inability to concentrate, After
exposure to 53 per cent oxygen some degree of
relaxation was obvious despite the dullness and
fatigue which were objectively and subjectively
perceived. It will be remembered that in the
more severe anoxia produced by inhaling io per
cent to sa per cent oxygen, McFarland and Baraeh
(jg) found more severe deterioration in
psychoneurotic patients than in the control
group, with mort marked physiological impairment
as well. Apparently, the milder degree of
oxygenwant used in this study was not sufficient
to produce marked physiological changes. In 4
patients, the effect of 13 per cent oxygen was
none or only a slight decrease in efficiency; in
patients there was an improved response,
apparently related to freedom from their usual
preoccupations.

The actual results of the "retention and
recall" testa upon which we base our conclusions
can best be illustrated by recording the
following representative series of observations:
For these studies we used the following two
stories for both groups. When one story was used
before the experiment, the other was used
after.

1) Weakened by rain, the front of a three
story brick house collapsed today. The wall
dropped like a curtain revealing Mr. Lester
dressing and Mr. Reed in bed. They were the only
occupants. "Is it time to get up?" Mr. Reed just
asked. The crash came, and Mr. Lester shouted
"yes." They were stranded when the stairway gave
way, and were rescued by firemen with
ladders.

2) Olaf Nelson died here today of burns
suffered when a match ignited his grass skirt in
a hula dance comedy during the American Legion
Convention. District Attorney Moore lighted a
cigarette and tossed the match. Brown
interviewed fifteen witnesses who said Moore
deliberately tossed the match to Nelson's
costume.

Student Group

Mr. L. Story before the experiment: Weakened
by rain the front of a brick house collapsed
today. There were two occupants, two occupants
were revealed. Mr. Lester standing up, and Mr.
Reed in bed. "Is it time to get up?" Mr. Reed
asked and Mr .... Wall... then the wall
collapsed and Mr. Lester said "yes." The
stairway ... they could out escape by the
stairway because that was blocked. The firemen
rescued them with ladders.

Mr. L. Story after 3 hours exposure to 13
per cent oxygen: Nelson suffered from injuries
... I think you said ... well, caused by burning
skirt made of grass. I think you said the
accident or incident happened on the ou said you
did not say an Island, you were niore specific
about it, you said the Island. It happened on
the Jslaod of Honolulu. I don't remember if you
said at the beach or no the beach ... the beach
... or whether the beach came in when the
District Attorney charged Morgan. District
Attorney charged Morgan .. . . ou, District
Attorney charged that Morgan was smoking on the
beach near by. I know you did not say Nelson . .
. you said him. Now next sentence is Mr. Brown
questioned ss witnesses, who said he was smoking
who saw him smoke a cigarette, who saw the
cigarette tossed at him.

Mr. B. Story before the experiment: Weakened
by rain the wall of a three story brick house
fell down and revealed Mr. Reed in bed and Mr.
Lester getting dressed. Mr. Reed asked, "Is it
time to get up?" Then a loud crash revealed that
the stairway gave way and they were left
stranded. That's all.

Mr. B. Story after the experiment: I did not
get too much of the story. I don't know much.
Some one by the name of Nelson committed a
murder, or something. There is something of hula
dance .... I don't know how it came in ... and
then District Attorney Brown had something to do
with the ease. He questioned somebody that's all
I can make out.

Patient Group

Mr. F. Story before the experiment: After
the front wall of building or the front part was
weakened by rain it collapsed ... those are not
the words. I am rephrasing ... revealed.... T
make two sentences of it ... Mr. Lester. I don't
want to say Mr. just Lester, dressing and Reed
in bed. Just before it happened Reed asked, I
don't know whether asked Lester, or just asked.
Whether it's time to get up. I asn beginning to
think whether they were in the same room or
different parts of the building. I don't recall
now. Costing back to the story of course if they
were in different parts of the building. well
... story ... of course would fall namely before
Lester had a chance to answer the crash occurred
... but I'll stick to central idea. I'll have to
say they were in the same room . . . greater
probability in my miud .. . . They were stranded
either when the stairway was blockaded or had
collapsed.

Mr. F. Story after the experiment:

Olaf Nelson died today of burns suffered
when the grass skirt which he was wearing during
a hula dance which he was doing during an
American Legion comedy ignited. Mr. Moore tossed
the match after lighting a cigarette. District
Attorney Brown after interviewing 40 witnesses,
I think ... I know. all right I think I am
making up his skirt was ignited wUe he was doing
orne of this . . . said he will hold Brown
because he felt that Moore deibcrately held the
match to Nelson's kirt.

Mr. S. Before the experiment: I am orry,
it's hard for me to start. It's a wall that
collapsed of a building It's about a wall .... I
don't recall the details .... The last sentence
you said one person asked, the other answered
'yes" and the wall collapsed.

Mr. S. After the experiment: Nelson DIaf
died today of burns suffered while his skirt was
ignited while he was doing o dance. District
Attorney Brown said that he will press charges
of manslaughter against Moore, which supposedly
ignited a cigarette and tossed the match at
Nelson Olaf. There are a witnesses that claim
that Moore deliberately ignited Nelson's
skirt.

In comparing the average results of both
experimental groups we find the poorest
performance of the student group exhibited fewer
errors than did the patient group in their best
performance. However, a comparison of
performance within each group shows that 15 of
57 in the student group exhibited an increase of
errors after exposure to 13 per cent oxygen
while ç of in the patient group showed a
decrease.

We have already mentioned that in the
student group we supplemented our "retention and
recall" test with observations using the
Rorschach test. Since the interpretation and
scoring of this teat is not yet standardized,
and considerable controversy still exists about
many pointa, we followed the original method of
Rorschach. It must be remarked that a number of
the students showed a marked deviation from what
is generally considered the normal. The results
of the Rorschach teat given immediately after
production of anoxia as compared with the
results obtained 4 to 8 weeks later, merely show
a swing in mood, where each individual follows
his inherent pattern.

Discussions

The suggestion has been made that the
mechanism of oxygen utilization may be impaired
in patients with psychoneurosis (34). The
disturbance in affective behavior produced by
inhalation of low oxygen mixtures indicates
clearly that an accustomed oxygen supply is
essential for a controlled emotional existence.
Although efficiency of memory appeared
superficially improved in of the 9 patients with
psychoneurosis, this must be considered in the
light of a very poor control; their nervous
preoccupations prevented them from attention to
the story and interfered with their ability to
concentrate. However, the impairment of those
inhibitions which are responsible for emotional
control was far more marked in the patient group
than in the students. Since the investigator who
recorded the actual testing was a young woman,
the release of the sexually inhibiting agency
was especially apparent. In a previous study
(9), release of sexual inhibition was observed
by a male investigator working with
undergraduate students, although to a much
smaller degree. The results of this
investigation are in harmony with the previously
reported findings of McFarland and Barach (34),
the patients with psychoneurosis are more
adversely affected by acute anoxia than normal
individuals.

The question still remains: is an organic
unfitness of the central nervous system in
respect to its utilization of oxygen a primary
factor in the production of psychoneurosis, or
does a disturbed psychoneurotic attitude
adversely affect the response to acute anoxia?
We mentioned earlier in this paper that a third
possibility exists in the interpretation of
psychosomatic disease, namely, that the
psychoneurotic pattern and an impaired mechanism
for handling anoxia may be branches from a
primary etiological stem, the exact nature of
which is still obscure. We are able at this time
merely to state that an accustomed oxygen supply
is a requirement for undisturbed mental
functioning.

The fact that apparently sane, wellbalanced
patients with chronic cardiac and respiratory
disease may temporarily show profound
disturbance in mental functioning as a result of
inhalation of 50 per cent oxygen has only been
briefly referred to in previous studies
(7,10,37), It is of interest that headache,
which is uniformly present as a result of acute
anoxia, is a frequent accompaniment of oxygen
treatment in patients with pulmonary emphysema.
When arterial anoxia has existed for a long
period and is of marked degree, irrationality
and delirium may occur within a period of
several hours; in other cases, a slowly
deepening stupor or coma may take place, with
periods of irrationality when awakened. In some
patients, lassitude and mental depression occur
without increased sleep. After a period of
several days to a week, the mentality clears and
the patient generally manifests a cheerful and
optimistic attitude. It seems definite that it
is the disturbance in the oxygen supply to which
the human subject has become accustomed that
upsets mental functioning.

In human subjects intoxicated by alcohol,
Palthe (35) found that inhalation of 100 per
cent oxygen overcame to a considerable extent
the effects of alcohol. These results have been
partially confirmed (5, 8), suggesting that
alcohol is at least to some extent an agent that
results in tissue anoxemia. In this instance, as
in adaptation to low and high oxygen
atmospheres, the individual may become
accustomed to a certain level of anoxia.

In an experiment on the treatment of
dementia precox, a psychiatric ward was kept at
an oxygen concentration of 50 per cent for two
and a half months (27). No effect on patients
with demen ti a precox was observed as a result
of this long-continued exposure to a high oxygen
atmosphere; the arterial oxygen saturation in
this study was within the range of normal. The
male attendants were unfortunately not studied
systematically from a psychological point of
view but no change in their behavior or attitude
was observed. 1h the clinical experience of the
senior author over a period of many years, no
mental changes have been observed in patients
treated with oxygen when previously existing
anoxemia was absent.

SUMMARY

The reactions of two groups of subjects, one
consisting of 17 medical students, the other of
patients from the mental hygiene clinic of
Bellevue Hospital, were studied prior to,
during, and after exposure to 13 per cent oxygen
for three hours. The basis for reaction
evaluation was the "retention and recall" test,
and in the student group, the Rorschach test as
well. In addition, alterations in behavior,
mood, speech and subjective complaints were
recorded.

In executing the experimental procedure, the
oxygen content of the atmosphere was gradually
lowered in one instance while in the other the
concentration was lowered abruptly to a 13 per
cent oxygen concentration. In the former
experiment a more prolonged period of elation
and a diminished frequency of somatic complaints
were observed. Aside from the aforementioned
differences, no other alterations were found to
exist as a result of the difference in the
technique of applying the reduced oxygen
concentration.

In the student group, during the 3 hour
inhalation of 53 per cent oxygen, all 57
complained of a frontal headache; mild
dizziness, yawning, sense of oppression,
pain in the joints and epigastrium, and tingling
sensation in the fingers and toes were frequent.
Changed perception of color and of their own
body and vague, undefined fears were observed.
Inability to concentrate occurred in all cases.
This was especially pronounced by the end of the
second hour. The perception of time was slower
in that the time intervals were evaluated as
shorter than actual. Mispronunciations were
noted several times. Fifty-nine per cent showed
shorter or longer periods of elation resembling
the hypomanic mood, followed by dullness,
drowsiness, and deep sleep. The ability to
distinguish between sleep and reality showed
some impairment. Forty per cent of the group did
not show any period of elation. Irritability and
dullness, resulting in listlessness and
especially poor performances on the
psychological tests, were noted. After the three
hour residence in 53 per cent oxygen, lethargy,
complaints of blankness, apathy, extreme
fatigue, sense of estrangement and detachment
from the world were observed in a great majority
of the subjects.

In the patient group, somatic complaints
were essentially the same as in the student
group except that they were less pronounced and
less frequent. A great majority of patients
expressed the suspicion that come stimulating
drug was added to the gas mixture, and they
expressed a fear of death by suffocation during
residence in the hood. Fifty-three per cent of
the patients exhibited a prolonged period of
excitenient, extreme productivity, lack of
inhibitions, frank sexual advances, sensations
of well being, exaggerated self esteem,
overactivity, restlessness and threatening
behavior. i'he remaining forty-seven per cent of
the patients did not show any period of
excitement. They were irritable, dull and drowsy
from the eisd of the first hour, and reniained
so throughout the experiment.

The students made 45.4 per cent more errors
in the "retention and recall" test after
inhalation of 53 per cent oxygen as compared
with their nonxial test. Errors in the test
occurred in 15 of the 17 students. 'fisc number
of added words accounted for the poor
performance. The added words expressed
hesitation, perseveration, uncertainty,
confabulation, and elaboration-a state closely
related to organic confusion.

The patient group showed 19.2 per cent less
errors as conspared with their normal test. The
number of added words, reflecting their usual
preoccupations, was the chief reason for this
high percentage of errors in the normal test. In
ç of 9 patients, the efficiency of
response was better after inhalation of 13 per
cent oxygen. Some degree of emotional relaxation
was observed after the exposure to lowered
oxygen.

Comparing the performances of both groups we
find that the patients made 10 per cent more
errors in the normal test as compared to the
normal test of the students. Furtherissore, the
best performance of the patients, i.e., after
the exposure to low oxygen, still showed 68 per
cent more errors than the best perfonsiance of
nsedical students in their normal test. 'fhe
results with the Rorschach test (13) after the
exposure to low oxygen as compared with the test
done to 8 weeks later showed only a superficial
change. The differences observed indicated a
swing in mood. Eleven of seventeen students
manifested a hypomanic state without any actual
dilatation of personality, that is merely a
state of elation. The remaining six students
exhibited a tendency toward depression. Reduced
ability to form new and original associations
was noted. The Rorschach test has sobstantiaced
the results obtained by objective observation
and by the "retention and recall" test in that
every individual follows his inherent pattern.
Anoxia nsereiy exposes and aggravates the
pre-existing tendency.

CONCLUSIONS

Variations in the oxygen concentration of
the inspired air, beyond that to which the
individual is accustomed, result in marked
changes in mental functioning. This disturbance
in mental functioning takes place in normal and
psychoneurotic subjects exposed to inhalation of
low oxygen atmospheres, and also in patients
with previously existing anoxia exposed to high
oxygen atmospheres. In the present study,
observation of 17 medical students who breathed
an atmosphere of 13 per cent oxygen
(corresponding to an altitude of 12,400 feet)
for three hours revealed marked changes in
affective behavior, with impairment of emotional
control, in 59 per cent elation and flightiness,
terminating in lethargy, and in 41 per cent
mental dullness from the beginning. The
"retention and recall" test in 15 of the 17
students showed a larger incidence of errors and
impaired memory after exposure to 13 per cent
oxygen for 3 hours.

The patients after inhalation of the low
oxygen mixture revealed an even more marked lack
of emotional restraint, with feelings of
exaggerated self-esteem and sexual
pre-occupations. Their mood ultimately changed
from that resembling a hypomanic state to
dullness and lethargy. Those patients (4 of 9)
who did not show elation at the start were dull
and lethargic from the beginning. The number of
errors in the "retention and recall" test showed
considerable variation before and after exposure
to inhalation of 13 per cent oxygen, in of 9
patients being better in the low oxygen
atmosphere. The greater degree of relaxation
which the low oxygen atmosphere induced appeared
to free thens from their usual preoccupations,
and make for a superficially better intellectual
performance. However, in respect to insight,
judgment and control of emotions, more marked
impairment was uniformly present than in the
studeist group.

The results of inhalation of 13 per cent
oxygen (corresponding to an altitude of 12,400
feet) reveal especially that an emotional
release, with diminished reason, memory and
judgment, follows exposure to moderate oxygen
deficiency for a three hour period, both in
psychoneurotic patients and in normal
individuals.

The inhalation of high oxygen atmospheres to
patients with previously existing chronic anoxia
may also produce a profound disturbance in
mental functioning. Irrationality, stupor and
delirium may take place within three hours
exposure to 50 per cent oxygen. When these
patients become acclimatized to their increased
oxygen tension, the mental disturbance
disappears, frequently with the appearance of a
cheerful and optimistic mental state.